Why is Apple Pay not available in India? And is there any scope for it in near future?

See -> About billing for Apple subscriptions and media products in India

About billing for Apple subscriptions and media products in India - Apple Support

India

•           Apple ID balance (from adding funds)

•           Net Banking4 (adding funds only)

•           UPI4 (adding funds only)

You can use / pay with your Apple ID balance, see the following Apple articles: 

Add money to your Apple ID balance

Add money to your Apple ID balance - Apple Support (IN)

What you can buy with your Apple Gift Card or Apple ID balance

What you can buy with your Apple Gift Card or Apple ID balance – Apple Support (UK)

How to redeem your Apple Gift Card or App Store & iTunes gift card

How to redeem your Apple Gift Card or App Store & iTunes gift card – Apple Support (UK)

And is there any scope for it in near future?

We don't know, we are also users of Apple products & services like you.